Look closely at cocktail in the East End (7)
I believe the answer is:
eyeball
'look' is the definition.
(I know this)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for eyeball that I've seen before include "One faces one in confrontation" , "Watch" , "Spherical optical organ" , "something in orbit" , "Socket filler" .)